The present invention relates to an evaporator used in a vehicular air conditioner, which is a refrigeration cycle to be mounted on an automobile, for example, and to a vehicular air conditioner using the same.
Herein and in the appended claims, the upper and lower sides of FIGS. 1 to 4 and 9 will be referred to as “upper” and “lower,” respectively.
There has been known an evaporator used in a vehicular air conditioner (see FIG. 12 of Japanese Patent Application Laid-Open (kokai) No. 2009-156532). The known evaporator includes a pair of header tanks which are disposed apart from each other in the vertical direction. A plurality of tube rows are disposed between the header tanks such that they are spaced from one another in an air-passing direction. Each tube row includes a plurality of heat exchange tubes which are disposed such that their longitudinal direction coincides with the vertical direction and they are spaced from one another in the longitudinal direction of the header tanks. Each header tank has leeward and windward header sections which are juxtaposed in the air-passing direction. At least one tube row is disposed between the leeward header sections of the two header tanks, and at least one tube row is disposed between the windward header sections of the two header tanks. Opposite ends of corresponding heat exchange tubes are connected to the leeward header sections of the two header tanks, and opposite ends of the remaining heat exchange tubes are connected to the windward header sections of the two header tanks. A refrigerant inlet is provided at one end of the leeward header section of one header tank, and a refrigerant outlet is provided at one end of the windward header section of the header tank, which end is located on the same side as the one end of the leeward header section. Each of the tube row connected to the leeward header sections of the two header tanks and the tube row connected to the windward header sections of the two header tanks includes a downward flow tube group and an upward flow tube group provided alternatingly. The downward flow tube group is composed of a plurality of heat exchange tubes through which refrigerant flows from the upper side toward the lower side. The upward flow tube group is composed of a plurality of heat exchange tubes through which refrigerant flows from the lower side toward the upper side. The refrigerant having flowed into the evaporator through the refrigerant inlet is caused to pass through the heat exchange tubes of all the tube groups and flow out from the refrigerant outlet. Each of the furthest tube group of the leeward tube row which is furthest from the refrigerant inlet and the furthest tube group of the windward tube row which is furthest from the refrigerant outlet is a downward flow tube group. A single path is formed by the two furthest tube groups juxtaposed in the air passing direction. Compartments respectively communicating with the furthest tube groups of the two tube rows are provided in the leeward and windward header sections of the upper header tank. The two compartments communicate with each other through a communication hole provided in a partition portion between the two compartments.
Incidentally, the evaporator disclosed in the publication may be used in an inclined state as viewed from the outside in the longitudinal direction of the header tanks. In such a case, due to the influence of gravitational force, a larger amount of refrigerant flows into a compartment located on the lower side, which is one of the two compartments of the upper header tank with which the two furthest tube groups communicate. As a result, the amount of refrigerant which flows into the heat exchange tubes of the furthest tube group communicating with the compartment on the lower side becomes larger than the amount of refrigerant which flows into the heat exchange tubes of the furthest tube group communicating with the compartment located on the upper side. Accordingly, imbalance occurs between the amount of refrigerant flowing through the heat exchange tubes located on the leeward side in the path formed by the furthest tube groups and the amount of refrigerant flowing through the heat exchange tubes located on the windward side in the path, whereby the performance of the evaporator may deteriorate.